Transcriptomic and lipidomic profiling of eicosanoid/docosanoid signalling in affected and non-affected skin of human atopic dermatitis patients.

Lipoxygenases (LOX) and cyclooxygenase (COX) are the main enzymes for PUFA metabolism to highly bio-active prostaglandins, leukotrienes, thromboxanes, lipoxins, resolvins and protectins. LOX and COX pathways are important for the regulation of pro-inflammatory or pro-resolving metabolite synthesis and metabolism for various inflammatory diseases such as atopic dermatitis (AD). In this study, we determined PUFAs and PUFA metabolites in serum as well as affected and non-affected skin samples from AD patients and the dermal expression of various enzymes, binding proteins and receptors involved in these LOX and COX pathways. Decreased EPA and DHA levels in serum and reduced EPA level in affected and non-affected skin were found; in addition, n3/n6-PUFA ratios were lower in affected and non-affected skin and serum. Mono-hydroxylated PUFA metabolites of AA, EPA, DHA and the sum of AA, EPA and DHA metabolites were increased in affected and non-affected skin. COX1 and ALOX12B expression, COX and 12/15-LOX metabolites as well as various lipids, which are known to induce itch (12-HETE, LTB4, TXB2, PGE2 and PGF2) and the ratio of pro-inflammatory vs pro-resolving lipid mediators in non-affected and affected skin as well as in the serum of AD patients were increased, while n3/n6-PUFAs and metabolite ratios were lower in non-affected and affected AD skin. Expression of COX1 and COX-metabolites was even higher in non-affected AD skin. To conclude, 12/15-LOX and COX pathways were mainly upregulated, while n3/n6-PUFA and metabolite ratios were lower in AD patients skin. All these parameters are a hallmark of a pro-inflammatory and non-resolving environment in affected and partly in non-affected skin of AD patients.

Bortezomib treatment diminishes hazelnut-induced intestinal anaphylaxis in mice.

Food allergy is a common health problem and can cause anaphylaxis. Avoidance of the offending food allergen is still the mainstay therapeutic approach. In this study, we investigated the role of plasma cell reduction by proteasome inhibition in a murine model of food allergy and examined the impact of this treatment on the systemic and local immune response. For this purpose, intestinal anaphylaxis was induced in BALB/c mice with the food allergen hazelnut, in conjunction with different adjuvants (alum and Staphylococcal enterotoxin B SEB) and different administration routes (oral and intraperitoneal). In both models, allergy symptoms were observed, but the clinical severity was more pronounced in the hazelnut-alum model than in the hazelnut-SEB model. Accordingly, allergen-specific immunoglobulin E (IgE) against hazelnut was detectable, and mast cell protease-1 in serum was increased after allergen provocation. Treatment with the proteasome inhibitor bortezomib reduced plasma cells and resulted in an abolishment of hazelnut allergen-specific IgE, which was associated with amelioration of clinical symptoms as well as a significant decrease in both CD19(+) and follicular B lymphocytes. Our data demonstrate the importance of allergen-specific IgE in food allergy and point to B cells as potential therapeutic targets for its treatment.

Dietary polyunsaturated fatty acids and non-digestible oligosaccharides reduce dermatitis in mice.

BACKGROUND: Oral administration of specific food ingredients can modify mucosal and systemic inflammatory processes. Such food components are fatty acids or carbohydrates. Nevertheless, little is known about the impact of oral administration of polyunsaturated fatty acids (PUFA) and non-digestible oligosaccharides on allergen-induced dermatitis. METHOD: In this pilot study, skin inflammation was induced by serial epicutaneous OVA applications in OVA-sensitized mice. In parallel, mice were fed with solid food containing arachidonic acid/docosahexaenoic acid (AA/DHA), galactooligosaccharide/polydextrose (GOS/PDX) or their combination. Skin lesions were assessed by clinical skin score, but also skin barrier parameters, immunohistochemical analyses, and local cytokine expression profile. RESULTS: Both dietary AA/DHA and GOS/PDX significantly ameliorated the severity of allergen-induced dermatitis. The clinical improvement upon oral AA/DHA and GOS/PDX supplementation was associated with a reduction in transepidermal water loss and reduced KI-67 expression in the skin. Lesional CD8+ and mast cells were reduced in all treatment groups, but appeared to be most pronounced in combined AA/DHA/GOS/PDX-treated mice. Moreover, in GOS/PDX-treated mice, IFNγ and TGFß expression was increased in skin lesions. CONCLUSION: Dietary supplementation with DHA/AA and GOS/PDX ameliorates symptoms of allergen-induced dermatitis and may thus be beneficial in the dietary management of human atopic eczema.

Oral administration of Escherichia coli Nissle 1917 prevents allergen-induced dermatitis in mice.

BACKGROUND: The prevalence of allergies has been linked to Western life style factors including a decrease of microbial exposure. Probiotics, such as Escherichia coli Nissle 1917 (EcN), have been shown to be beneficial for prevention and treatment of several chronic inflammatory diseases. OBJECTIVE: The aim of this study was to investigate the impact of oral EcN administration on development and outcome of allergen-induced dermatitis. METHODS: In sensitized BALB/c mice, skin inflammation was induced by topical allergen application. EcN was administered orally in a preventive manner. Severity of dermatitis was analysed by evaluation of skin score, local cellular and cytokine profile. The systemic immune response was assessed by analysis of immunoglobulins and allergen-dependent cytokine response. RESULTS: Oral EcN administration improved allergen-induced dermatitis dose-dependently. In parallel, a reduction of epidermal thickness and infiltrating immune cells together with an enhanced number of forkhead box P3 (Foxp3)(+) cells and a trend of increased IFNγ, IL-10 and TGFß expression was detected in eczematous skin. In allergen-stimulated splenocytes reduced IL-4 and IFNγ along with an elevated IL-10 production and a tendency to an increased TGFß secretion were observed. CONCLUSIONS: Our findings indicate that EcN alters the local allergen-induced immune response by increase of Foxp3(+) cells and by favouring an immunoregulatory cytokine pattern. Thus, oral administration of EcN might be an effective strategy in prevention and potentially therapy of allergic inflammatory skin diseases.

Dietary docosahexaenoic acid in combination with arachidonic acid ameliorates allergen-induced dermatitis in mice.

OBJECTIVE: In this study, we investigated the impact of dietary docosahexaenoic (DHA) and arachidonic acid (AA) on development and severity of allergen-induced dermatitis. STUDY DESIGN: In sensitized mice, skin inflammation was induced by ovalbumin. Mice received either a diet containing 0.015% DHA, 0.029% AA or the combination of both. The severity of dermatitis was evaluated by using a clinical skin score (CSS), followed by immunohistologic and cytokine analysis. To unravel potential mechanisms, interleukin (IL)-4 or tumor necrosis factor α-stimulated keratinocytes from the cell line Kera-308 was cultured with different DHA/AA compositions and analyzed regarding proliferation and cytokine production. RESULTS: Dietary DHA/AA significantly improved the severity of allergen-induced dermatitis as the CSS was reduced by 36 ± 23% (p=0.005). Furthermore, reduced epidermal KI67 expression, increased number of forkhead box P3(+) cells, and elevated IL-10 expression were determined in skin lesions of dietary-treated mice. Correspondingly, in vitro DHA/AA-treated keratinocytes exhibited increased IL-10 expression and produced less thymic stromal lymphopoietin. CONCLUSION: Dietary DHA/AA supplementation leads to a significant amelioration of allergen-induced dermatitis. This was accompanied with the presence of increased regulatory T cells and IL-10 expression in lesional skin. Moreover, we identify keratinocytes, which play a crucial role in the regulation of skin inflammation, as important targets of DHA/AA supplementation. Future studies are needed to clarify whether DHA/AA acts directly or whether its biologic active metabolites are responsible for these findings. This may unravel novel therapeutical compounds for allergen-induced dermatitis.

Inhibition of IgE production by docosahexaenoic acid is mediated by direct interference with STAT6 and NFκB pathway in human B cells.

Nutrition can modify the onset or severity of diseases and recent changes in eating habits are supposed to promote immunoglobulin (Ig) E-dependent disorders. The n-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) possesses immunomodulatory properties and has been shown to influence chronic and allergic inflammatory disorders in vivo. Here, we examined the impact of DHA on primary human B cells to elucidate its potential role in direct regulation of IgE production and the underlying mechanisms of action. Therefore, cells were stimulated with anti-CD40/interleukin (IL)-4 in the presence of DHA. Subsequently, Ig production, generation of antibody secreting cells, epsilon-germline transcript (ɛGLT) and activation induced desaminase (AID) expression as well as IgE relevant signaling pathways were analyzed. Our results reveal that DHA inhibits IgE production (75±14%) and, depending on concentration, the differentiation of IgE secreting cells (59±27%). The reduction of IgE is accompanied by a direct inhibition of the switching process indicated by decreased ɛGLT and AID transcription. DHA causes both a reduced CD40 dependent nuclear factor κB-p50 translocation into the nucleus and a decreased IL-4 receptor expression which was associated with a reduction of IL-4 driven signal transducer and activator of transcription 6 phosphorylation. Taken together, DHA inhibits IgE production of human B cells by direct interference with both the CD40 and the IL-4 signaling pathway. The data provide one explanation for the anti-allergic role of DHA at the molecular level.

Interleukin-17A promotes IgE production in human B cells.

Recently the Th1/Th2 concept has been revised and Th17 cells have been implicated in allergy. Despite clear correlative evidence, the cellular and molecular basis for the connection between increased IL-17A and IgE in allergy has not been elucidated. Here we show using flow cytometry that allergic patients have higher numbers of IL-17A+ cells compared to nonallergic donors. The selective removal of IL-17A+ cells from peripheral blood mononuclear cells of allergic donors after an IL-17A secretion assay reduces IgE levels, whereas re-addition of recombinant IL-17A restores it, as measured by ELISA, showing their important functional implication for IgE production. In addition, IL-17A directly promotes the differentiation of IgE-secreting cells and IgE production upon anti-CD40/IL-4 costimulation, as shown by enzyme-linked immunospot technique and ELISA. IL-17A triggers rapid degradation of IκBα and subsequent translocation of NF-κB into the B-cell nucleus, followed by transcription of epsilon germ-line, activation-induced cytidine deaminase, and IFN regulatory factor 4, as analyzed by flow cytometry, western blot, and quantitative real-time RT-PCR, respectively. Our study shows that IL-17A+ cells promote IgE production and that IL-17A exerts its pro-allergic effect directly at the level of B cells. Therefore, IL-17A might be a target for the treatment of IgE-dependent diseases, including atopic dermatitis.